I'm in the process of designing my site and I have a few questions on designing principles:

Is it best to optimize my site for 800x600 or 1024x768?
Do I assume that most of my visitors will be 56k or DSL? I spoke to a friend who insisted that most users are on DSL now so websites can afford to be a bit more graphics heavy but I feel like I should streamline more.
Ideally, how long should a site take to load?

Thanks y'all.